Ion implantation is a technique for introducing conductivity-altering impurities into a workpiece such as a wafer or other substrate. A desired impurity material is ionized in an ion source of an ion beam implanter, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the workpiece. The energetic ions in the beam penetrate into the bulk of the workpiece material and are embedded into the crystalline lattice of the workpiece material to form a region of desired conductivity.
Conventional ion beam implanters often include a number of extraction electrodes, including a suppression electrode and a ground electrode, configured to extract an ion beam from an ion source and to manipulate (e.g., focus and/or direct) the ion beam in a desired manner. The extraction electrodes are commonly mounted on an electrode positioning system including a motorized manipulator arm for facilitating selective movement of the extraction electrodes relative to the ion source. For example, if an ion beam is out of focus when initially extracted from the ion source, the manipulator arm may reposition the extraction electrodes in a corrective manner to focus the ion beam in a desired manner.
Due to a large difference in electrical potential between a ground electrode and a suppression electrode during operation of an ion implanter electrically insulating the electrodes from one another is performed to prevent or mitigate the flow of electrical current therebetween. Particularly, the ground electrode is separated from the suppression electrode with an electrical insulator. A shortest distance measured along a surface of the insulator between the electrodes, commonly referred to as a “tracking distance,” achieves a desired degree of physical separation and electrical insulation between the electrodes. Maintaining a specific distance, hereinafter referred to as a “focal distance,” between a ground electrode and a suppression electrode is generally performed in order to focus an extracted ion beam in a desired manner.
Focal distances are typically shorter than tracking distances. Thus, in order to maintain a desired focal distance between a ground electrode and a suppression electrode while simultaneously providing a tracking distance of desired length between the electrodes, ground electrodes and a suppression electrodes are often coupled to one another using complex mounting arrangements including multiple connective and supportive structures (e.g., support arms, mechanical fasteners, etc.) having associated manufacturing tolerances. When aggregated, these manufacturing tolerances can result in an undesirable offset or eccentricity between a ground electrode and a suppression electrode, adversely affecting the focus and/or alignment of an extracted ion beam. Additionally, the various supportive and connective structures used to couple a ground electrode and a suppression electrode may be formed of various materials having different coefficients of thermal expansion, and/or may be subject to uneven heating during operation of an ion implanter. This may lead to incongruous thermal expansion and contraction of the supportive and connective structures, further exacerbating eccentricity between the ground electrode and suppression electrode.
It is with respect to these and other considerations the current improvements may be useful.